I am looking into buying a bellmouth invidia downpipe for my 06 wrx for 100 bucks.. will this work good w/ stock cat back? Will I have to do anything with the computer?

 

it will work with your stock exhaust. You SHOULD get engine management if you do this. Without any type of management, you will run into boost creep and fuel cut and possible lean conditions. An Accessport is your best bet to solve this.

 

but if you cant afford the engine management yet atleast get a boost gauge to monitor your boost creep to see if and when its a problem. pick up a gauge from glowshift for like $30 temporarily, it will get the job done.

 

where did you find a downpipe for 100 bucks invidia nontheless?

 

I got a ERZ downpipe with stock muffler and it DOES NOT boost creep at all. Matter of fact it seems to run like stock but with that spooling sound.

ERZ downpipe and muffler not attached (straight pipe) and stock 2.5 exhaust, it still does not boost creep. It will boost faster but not creep to 14 or 13.

 

yea boost creep is pretty minimal with a add on DP. normally occurs in higher RPM's and in higher gears. I would definately get a boost gauge if you dont have the stocker though just to make sure nothing is out of place.

 

Thats how lean you will be running.
If you can not get it tuned, Save yourself the B.S. DONT mess with the car.
These cars do not make cheap HP without blowing up. A tune should be #1 on the list. You will gain more from a tune on a oem car, then adding just a cheap downpipe.

 

wow, that is a sparatic sheet. The boost creep does not affect everyone. Even with a Cobb stage two tune, I am getting it at 5000rpm in 4th gear.

 

^
That is good proof of why a tune after a catless down pipe
is so detrimental.